I need a pair of shift registers; for expanding number of I/O pins of my microcontrol

[hkBattousai]

I want to expand number of I/O ports of my microcontroller. For this purpose, I want to use a pair of shift registers (one for output: "serial in - parallel out"; and one another for input: "parallel in - serial out"). But there is one problem, I have to connect parallel I/O pins of shift registers, so I need a special shift register which can be disabled, and when disabled it must give high impedence at its pins.

I searched using Google, but couldn't find an IC like this.
I will apreciate if you could suggest me one.
Or, maybe, should I prefers a different method for this port expension?

 

[ericgibbs]

I want to expand number of I/O ports of my microcontroller. For this purpose, I want to use a pair of shift registers (one for output: "serial in - parallel out"; and one another for input: "parallel in - serial out"). But there is one problem, I have to connect parallel I/O pins of shift registers, so I need a special shift register which can be disabled, and when disabled it must give high impedence at its pins.

I searched using Google, but couldn't find an IC like this.
I will apreciate if you could suggest me one.
Or, maybe, should I prefers a different method for this port expension?

hi,
Why do you need a 'hardware' parallel to serial device.?
You can do serial bit output of a byte from a register on one PIC pin.

 

[Pommie]

If you explain what you are trying to do there may be a better solution.

Mike.

 

[hkBattousai]

hi,
Why do you need a 'hardware' parallel to serial device.?
You can do serial bit output of a byte from a register on one PIC pin.

Yes I can send serial bits and convert them using a serial to parallel shift register, but how can I receive parallel data into those a serial stream.
Don't I need a parallel to serial convertor for that?

If you explain what you are trying to do there may be a better solution.

I will post the schematics soon.

 

[caster.cp]

Serial-in / Parallel-out - 74' 595 - 8 bits serial in / parallel and serial out (has internal latch and three-state outputs)
74' 295 - 4 bits parallel and serial in / parallel out (also has internal latch and three-state outputs)
74' 594 - the same as the '595, but with totem-pole outputs and with two asynchronous resets (the '595 has only one)
74' 198 - 8 bits bidirectional parallel and serial in / parallel out (totem-pole outputs)
74' 164 - 8 bits serial in / parallel out (totem pole outputs, asynchronous reset)
74' 95 - 4 bits serial and parallel in / parallel out (totem pole outputs)
74' 194 - 4 bits serial and parallel in / parallel out (bidirectional, totem pole outputs, asynchronous reset)

Parallel-in / Serial-out - 74' 165 - 8 bits parallel and serial in / serial out (totem pole outputs, no reset)
74' 589 - 8 bits parallel and serial in / serial out.


I normally use the 595 and the 165 to execute parallel/serial conversion. I'm used to them. The 595 is a little bit annoying to drive with just one clock input, because of its internal latch, but once you get the hang of it you're fine.

Needless to say that you should stick, at least, with the not-so-new families LS, HC(T) or AC(T)...

 

[ericgibbs]

Yes I can send serial bits and convert them using a serial to parallel shift register, but how can I receive parallel data into those a serial stream.
Don't I need a parallel to serial convertor for that?



I will post the schematics soon.

hi,
You can buy parallel to serial shift registers. one type is HEF4021, a 8 bit parallel load with a clocked serial output.

Drive the S/R clk with one PIC pin and read the S/R data pin with another PIC pin into a PIC register.

EDIT:
Another option is the HEF4512, 8 input mux with 3 state output.

 

[hkBattousai]

Maybe out of topic, but I didn't want to open a new topic for this,
Can you suggest me a very cheap 24-bit A/D convertor. I don't need much of sample rate.
Will work with inputs in [0V, 5V] range.

I don't want to ask in forum everytime I need an IC, how can I find parts on my own? Is there any search engine, or any other search method for this purpose?

 

[BrownOut]

hkBatousai - would you consider changing your avatar? Thanks.

 

[hkBattousai]

hkBatousai - would you consider changing your avatar? Thanks.

Did so, how is the new one?

 

[BrownOut]

I like it! Thank you very much